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1.
Water Sci Technol ; 81(6): 1130-1136, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32597400

RESUMO

Heavy metal pollution has become one of the most serious environmental problems today. The preparation of magnesium hydroxy carbonate from low-grade magnesite, and the chemical precipitation of heavy metal wastewater with magnesium hydroxy carbonate as precipitating agent were undertaken. The removal efficiencies of heavy metals were improved by increasing the dose of magnesium hydroxy carbonate, and the applicable dose of magnesium hydroxy carbonate was 0.30 g for 50 mL of the wastewater (6,000 mg/L). The precipitation reactions proceeded thoroughly within 20 min. At this time, the removal efficiencies of heavy metals were above 99.9%. The final pH value was 7.1, the residual VO2+, Cr3+ and Fe3+ concentrations were 0.01, 0.05 and 1.12 mg/L, respectively, which conformed to the limit of discharge set by China (0.5-2.0 mg/L, GB 8978-1996). The precipitate was mainly composed of Fe2O3, V2O5 and Cr2O3, which can be recycled as secondary raw material for metallurgical industry. The treatment of the heavy metal wastewater with magnesium hydroxy carbonate was successful in decreasing the concentrations of VO2+, Cr3+ and Fe3+ in wastewater.


Assuntos
Metais Pesados , Águas Residuárias , Carbonatos , Precipitação Química , China , Magnésio
2.
J Environ Manage ; 264: 110419, 2020 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-32250884

RESUMO

The stability of carbonate products resulting from microbially induced carbonate precipitation (MICP) under acid rain is under question. The present study investigated the stability of CaCO3 precipitated by MICP in soil under simulated acid rain (SAR). Soils were treated continuously for two months with four SAR pH levels: 3.5, 4.5, 5.5, and 7.0. During SAR, biostimulation using nutrient broth containing urea and calcium chloride was adopted to ensure CaCO3 precipitation. At the end of treatments, soil samples from top and bottom layers were analyzed for bacterial diversity by Illumina MiSeq sequencing, Fourier transform infrared (FTIR) spectroscopy for identification of chemical functional groups related to calcite precipitation, and X-ray diffraction (XRD) for identification of the main crystalline phases. The analysis identified several ureolytic bacteria mainly from Arthrobacter and Sporosarcina genera in SAR-treated soils accelerated with biostimulation, and urease quantities of greater than 300 mg NH4+ per kg soil at all pH levels. The precipitation of CaCO3 was pronounced and its stability was maintained even when the pH was as low as 3.5. The results obtained in this study are helpful to the scientific community to ensure the immobilization of heavy metals with microbial carbonate precipitation in soil under acid rain.


Assuntos
Chuva Ácida , Sporosarcina , Carbonato de Cálcio , Carbonatos , Precipitação Química , Solo
3.
Chemosphere ; 250: 126325, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32234625

RESUMO

Atmospheric carbon dioxide (CO2) imbalance due to anthropogenic emissions has direct impact in climate change. Recent advancements in the mitigation of industrial CO2 emissions have been brought about by a paradigm shift from mere CO2 capture onto various adsorbents to CO2 conversion into high value products. The present study proposes a system which involves the conversion of CO2 into high purity, low moisture, compact and large CaCO3 solids through homogeneous granulation in a fluidized-bed reactor (FBR). In the present study, synthetic solutions of potassium carbonate (K2CO3) and calcium hydroxide (Ca(OH)2) were used as sources of carbonate and precipitant, respectively. The effects of the degree of supersaturation (S) as chemical loading and influx flow rate (QT) as hydraulic loading on CaCO3 granulation efficiency were investigated. In the study, S was varied from 10.2 to 10.8 and QT from 40 to 80 mL min-1 while the operating pH and calcium-is-to-carbonate molar ratio ([Ca2+]/[CO32-]) were set at 10 ± 0.2 and 1.50, respectively. Results showed that carbonate ions end product distribution had a highest carbonate granulation efficiency at [Carbonate]G of 95-96% using S of 10.6 and QT of 60 mL min-1. Characterization of the granules confirmed high purity calcium carbonate. Overall, the transformation of industrial CO2 emissions into a valuable solid product can be a significant move towards the mitigation of climate change from anthropogenic emissions.


Assuntos
Carbonato de Cálcio/química , Dióxido de Carbono/química , Sequestro de Carbono , Carbonatos , Fenômenos Físicos , Potássio
4.
Chemosphere ; 251: 126254, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32155499

RESUMO

Due to its toxicity and persistence, pesticide pollution poses a serious threat to human health and the environment. Imidacloprid or IMD is an archetypal neonicotinoid insecticide commonly used to protect a variety of crops worldwide. The present study examines the applicability of two numerical tools -- artificial neural network (ANN) and response surface methodology - Box Behnken design (RSM-BBD) -- to model and optimize oxidative IMD degradation by sodium percarbonate (SPC). The influences of SPC dose, Fe2+ catalyst dosage, and solution pH on IMD removal were evaluated. An ANN composed of an input layer with three neurons, a hidden layer with eight optimum neurons, and an output layer with one neuron was developed to map the complex non-linear process at different levels. Seventeen designed runs of different experimental conditions were derived from RSM-BBD. These experimental conditions and their response values showed to be best fitted in a reduced cubic model equation. Sensitivity analyses revealed the relative importance of the various components: Fe2+ (40.4%) > pH (31.1%) > SPC dose (28.5%). The two model were highly predictive with overall coefficients of determination and root-mean-square errors of 0.9983 and 0.31 for ANN, while 0.9996 and 0.20 for RSM-BBD. Overall, the present study established ANN and RSM-BBD as valuable and effective tools for catalytic SPC oxidation of IMD contaminants. SPC is a cleaner alternative to other oxidants for pesticide degradation as it is non-toxic, safe to handle, and produces by-products that inherently exist in the natural water matrix.


Assuntos
Carbonatos/química , Modelos Químicos , Neonicotinoides/química , Redes Neurais de Computação , Nitrocompostos/química , Catálise , Oxidantes , Oxirredução , Projetos de Pesquisa
5.
Chemosphere ; 250: 126307, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32114349

RESUMO

The leaching characteristics of seven different recycled concrete aggregates (RCA) samples derived from building demolition waste, concrete pavement, stockpiled, and freshly crushed concrete were evaluated focusing on the effects of carbonation, liquid-to-solid ratio (L/S), and particle sizes. Batch water leach test (WLT), toxicity characteristic leaching procedure (TCLP), and synthetic precipitation leaching procedure (SPLP) were performed to assess the pH, electrical conductivity (EC), alkalinity, and the leached concentrations of Ba, Ca, Cr, Mg, and SO4 in RCA effluent. The leaching efficiency of the test methods at different RCA carbonation levels was also evaluated. Results indicated that the effluent pH, EC, and alkalinity decreased, while the leached fractions of elements increased with an increase in L/S ratio. An increase in calcium carbonate content tended to increase the leaching of Mg, Cr, and SO4. For highly carbonated RCA samples, effluent pH, EC, alkalinity, and Ca concentrations were higher for particle sizes of 1.19 mm-0.149 mm, while fresher RCA samples resulted in higher values from particles finer than 0.149 mm. Carbonated RCA samples leached higher Ca, Mg, and Ba in TCLP, whereas the maximum concentrations of Cr and SO4 were found in WLT effluent. For less carbonated RCA samples, Ca concentrations in WLT and TCLP effluents were comparable, SPLP leached higher amounts of Mg, Ba concentrations were maximum in WLT, and TCLP concentrations of Cr and SO4 were the most critical ones. TCLP alkalinity increased, whereas WLT and SPLP alkalinity decreased with an increase in calcium carbonate content of the RCA.


Assuntos
Materiais de Construção , Reciclagem , Carbonatos , Teste de Materiais , Tamanho da Partícula , Solubilidade
7.
Chemosphere ; 249: 126115, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32045756

RESUMO

The BCR sequential extraction scheme (SES), initially developed for soils and sediments, is frequently adopted to evaluate the environmental risks of municipal solid waste incineration (MSWI) fly ash. Within the procedure, metals are liberated from the matrix hosting them relying on the selectivity of the chosen chemical reagents or operation conditions. However, the effect of the high content of alkaline substances in MSWI fly ash on the selectivity of acetic acid to acid-soluble fraction metals was ignored. In this study, the feasibility of the BCR SES for evaluating MSWI fly ash was assessed by adjusting the acetic acid washing times in the acid-soluble extraction step. The metal fractionation, as well as mineralogy, morphology, and surface chemistry of the residues after three successive acid washing processes, were analyzed. The results reveal that only easily soluble salts, but not hydroxides, are entirely extracted after the first acid washing (pH∼12.0). Importantly, carbonates (generally reported as an indicator of the complete release of acid-soluble metals) are mostly decomposed only after the third acid washing (pH∼3.8). The incomplete dissolution of calcium carbonates in a single-step acid washing may convey misleading results of metal fractionation and underestimates the environmental risk of potentially toxic elements. Therefore, complete removal of carbonates should be employed as the endpoint of the acid-soluble fraction extraction step in the evaluation of MSWI fly ash. This work can help in selecting proper strategies for fly ash management and developing proper sequential extraction schemes for similar high-alkalinity hazardous waste risk assessment.


Assuntos
Incineração/métodos , Metais Pesados/análise , Carbono/química , Carbonatos/química , Fracionamento Químico , Cinza de Carvão/química , Material Particulado/química , Eliminação de Resíduos , Sais , Resíduos Sólidos/análise , Oligoelementos/análise
8.
Chemosphere ; 249: 126227, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32087456

RESUMO

Efficient lead removal from metal-containing wastewater, such as acid mine drainage (AMD), is an important step in environmental purification and secondary resources recovery. In this paper, a novel approach by mechanochemically activating CaCO3 through simply wet ball milling in metal-containing solution was developed, where selective Pb2+ precipitation in the form of PbCO3 was achieved based on its reaction with the CO32- from the activated CaCO3. By such milling operation, the removal efficiency of Pb2+ from aqueous solution could reach over 99%, while more than 99% Zn2+ (as well as Mn, Ni and Cd) was remaining in the solutions, demonstrating the feasibility and high effectiveness of precipitating Pb2+ and serving the purpose of recovering other metals without Pb impurity. The solubility differences between Pb carbonate and other carbonates of Zn, Mn, Ni or Cd were understood to be the main pathway and using CaCO3 would offer an easy operation and environmental friendly process to purify the metals-containing wastewater by precipitating Pb, compared with the difficulties when using alkaline neutralization to treat them. In addition, basic zinc carbonate (a zinc-containing ore waste) as an alternative precipitant to CaCO3 in the separation process was also confirmed to increase the zinc recovery in the solution while maintaining high Pb2+ removal efficiency.


Assuntos
Carbonato de Cálcio/química , Chumbo/química , Eliminação de Resíduos Líquidos/métodos , Carbonatos , Química Verde , Metais Pesados/análise , Mineração , Águas Residuárias , Água , Purificação da Água , Zinco/análise , Zinco/química , Compostos de Zinco
9.
Water Res ; 174: 115626, 2020 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-32101786

RESUMO

In this work, Fe(II) catalyzing sodium percarbonate (Fe(II)/SPC) was managed to facilitate waste activated sludge (WAS) dewatering for the first time. The results showed that after WAS was treated by 20 mg/g total suspended solids (TSS) Fe(II) and 50 mg/g TSS SPC, the water content of sludge cake (WCSC) by press filtration and capillary suction time (CST) dropped from 90.8% ± 1.6% and 96.1 ± 4.0 s (the control) to 55.6% ± 1.4% and 30.1 ± 2.5 s, respectively. The mechanism investigations indicated that four intermediates or products (i.e., •OH, H2O2, Fe(II), and Fe(III)) generated in the Fe(II)/SPC process were responsible for the improved WAS dewaterability, and •OH and Fe(III) were the two major contributors. It was found that •OH collapsed and fragmented extracellular polymeric substances, damaged cell wall and permeabilized cytoplasmic membrane, and transformed conformation of the extracellular proteins secondary structure via both affecting the hydrogen bond maintaining α-helix and cracking disulfide bond in cysteine residues while Fe(III), the oxidization product of Fe(II), decreased the surface electronegativity and water-affinity surface areas of WAS flocs. As a result, the bound water release, flocculability, surface hydrophobicity, drain capability, and flowability of WAS flocs were strengthened whereas the compact surface structure, colloidal forces, network strength, gel-like structure, and apparent viscosity of WAS flocs were weakened. In addition, Fe(II)/SPC process also reduced the recalcitrant organics and fecal coliforms in sludge, which facilitated land application of dewatered sludge. The findings acquired in this work not only deepens our understanding of Fe(II)/SPC-involved WAS treatment process but also may guide engineers to develop both effective and promising strategies to better condition WAS for dewatering in the future.


Assuntos
Esgotos , Eliminação de Resíduos Líquidos , Carbonatos , Compostos Férricos , Compostos Ferrosos , Peróxido de Hidrogênio , Água
10.
Dent Mater J ; 39(2): 181-186, 2020 Mar 31.
Artigo em Inglês | MEDLINE | ID: mdl-32037383

RESUMO

The molecular precursor method is an easy and simple method for coating thin carbonate-containing apatite (CA) films onto titanium surfaces. A molecular precursor solution containing ethanol, calcium-EDTA complex, and phosphate salt was dropped onto a titanium surface and then heated at 600°C for 2 h. An adherent thin CA coating was achieved. Animal implantation experiments showed that CA-coated implants had significantly higher bone-to-implant values than non-coated implants (p<0.05). The molecular precursor method was also used to coat three-dimensional titanium webs (TWs). Thin CA films could be coated inside the center area, as well as the surface of the TW, with excellent bone formation inside the CA-coated TW. Furthermore, the molecular precursor method was used to coat partially stabilized zirconia with CA. Better bone response was observed for CA-coated zirconia. From this, it is concluded that the molecular precursor method is useful for producing thin CA coatings on implant materials.


Assuntos
Implantes Dentários , Animais , Apatitas , Carbonatos , Materiais Revestidos Biocompatíveis , Propriedades de Superfície , Titânio
11.
Mar Pollut Bull ; 151: 110834, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-32056626

RESUMO

This research characterizes the temporal and spatial variability of the seawater carbonate chemistry on the near-shore waters of the northern Persian Gulf and Makran Sea. In general, normalized total alkalinity (nAT) showed a westward decrease along the coasts of Makran Sea and the Persian Gulf. Intertidal seawater was always supersaturated in terms of calcium carbonate minerals during the daytime. Rocky shore waters in the Persian Gulf were sinks for CO2 in the winter during the daytime. The nAT decreased from Larak to Khargu Island by 81 µmol/kg. As expected, the two hypothetical drivers of bio-calcification, i.e., Ω and the [HCO3-]/[H+] ratio, were significantly related at a narrow range of ambient temperature. However, as data were pooled over seasons and study sites, in contrast to ΩAr, the [HCO3-]/[H+] ratio showed a slight dependence on temperature, suggesting that the ratio should be investigated as a more reliable factor in future biocalcification researches.


Assuntos
Antozoários , Carbonatos , Recifes de Corais , Água do Mar/química , Animais , Carbonato de Cálcio , Ecossistema , Monitoramento Ambiental , Concentração de Íons de Hidrogênio , Oceano Índico
12.
Artigo em Inglês | MEDLINE | ID: mdl-32003307

RESUMO

Synthesis of hydroxyapatite coated activated carbon nanocomposite was carried out by in-situ chemical precipitation method. Different characterizations confirm that, hydroxyapatite successfully coated over activated carbon powder. Extensive sorption studies of U(VI) on the nanocomposite were conducted to know the effect of contact time, humic acid, carbonate, ionic strength and pH. The study revealed that, the composite material is a more efficient sorbent for U(VI) compared to precursors, which removes U(VI) ion without altering physicochemical properties of water. Sorption exhibits multilayer adsorption on heterogeneous surface and follows chemisorptions. Practical applicability of the material was demonsteted by spiking tap water with U(VI) ion at three different initial concentrations (50, 100 and 150 µg L-1) and the tap water was allowed to passed through a cartridge packed with composite. It was observed that, the concentration of U(VI) ion in eluted water reduced to 98.28%, 96.20% and 97.40%, respectively. This revealed that, the material possesses a huge potential for sequestrating dissolved U(VI) ion and can be used as alternate filtering material for dissolved U(VI) in complex natural water system.


Assuntos
Carvão Vegetal/química , Durapatita/química , Nanocompostos/química , Urânio/análise , Poluentes Radioativos da Água/análise , Purificação da Água/métodos , Adsorção , Carbonatos/química , Substâncias Húmicas/análise , Concentração de Íons de Hidrogênio , Modelos Teóricos , Concentração Osmolar , Pós
13.
J Environ Manage ; 260: 110054, 2020 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-32090807

RESUMO

The abatement of CO2 emitted from combustion is a hot research topic. Current CO2 capture techniques of adsorption, absorption, membrane separation and cryogenics involve high investment and operation costs. For moderate and high temperature exhaust gas, carbonation/decarbonation cycles offer an attractive alternative. An objective assessment method (screening index) was applied to select the most appropriate chemical reactions, with MgO and Mg(OH)2 being screened as having the highest potential. Macro-thermogravimetric experiments determined a CO2 capture yield between 60 and 70% for Mg(OH)2 at temperatures between 260 and 330 °C, and from 85 to 98% for MgO at temperatures of 400-440 °C. Reaction rates were measured for both MgO-CO2 and Mg(OH)2-CO2. The reaction kinetics are best fitted by the Jander 3D-diffusion approach. The Arrhenius equation is applied to the reaction rate constant, and both its activation energy and pre-exponential factor are determined. Integrating the Jander expression in the reaction rate equation enables to predict the CO2-capture conversion for any selected temperature and/or contact time.


Assuntos
Dióxido de Carbono , Carbonatos , Adsorção , Temperatura Alta , Temperatura
14.
J Environ Manage ; 256: 109938, 2020 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-31989976

RESUMO

Copper contamination in watercourses is a recent issue in countries where mining operations are prevalent. In this study, the application of copper precipitation through microbe-induced carbonate precipitation (MICP) was analyzed using urea hydrolysis by bacteria to evaluate precipitated copper carbonates. This article demonstrates the application of a copper precipitation assay involving Sporosarcina pasteurii (in 0.5 mM Cu2+ and 333 mM urea) and analyzes the resultant low removal (10%). The analysis indicates that the low removal was a consequence of Cu2+ complexation with the ammonia resulting from the hydrolysis of urea. However, the results indicate that there should be a positive correlation between the initial urea concentration and the bacterial tolerance to copper. This identifies a challenge in the industrial application of the process, wherein a minimum consumption of urea represents an economic advantage. Therefore, it is necessary to design a sequential process that decouples bacterial growth and copper precipitation, thereby decreasing the urea requirement.


Assuntos
Cobre , Sporosarcina , Carbonato de Cálcio , Carbonatos , Precipitação Química , Ureia
15.
Sci Total Environ ; 712: 136435, 2020 Apr 10.
Artigo em Inglês | MEDLINE | ID: mdl-31931213

RESUMO

Biochar has attracted wide interest due to its important role in the synthesis of functionalized carbon materials. Molten alkali carbonates (MC) pyrolysis as a novel mean was explored to obtain superior bamboo biochar compared with alkali impregnation pretreating bamboo powder associated with pyrolysis. The properties of biochar produced by MC pyrolysis were enhanced, suggesting an increase in BET surface area of 43.59 m2/g compared with non-pretreat biochar of 5.76 m2/g, and possessed preferable pore structure than the alkali impregnation one of 39.82 m2/g and 16.98 nm for catalyst support. Besides, pyrolysis temperature reinforced the porosity and the degree of carbonization as it rising, however, the optimized temperature for top-grade biochar materials was 450 °C. The MC weakened the hydrogen bonds network in bamboo powder acting a similar role just as alkaline pretreated, meanwhile neutralized the acid produced during pyrolysis process supported by the analysis of FTIR and TGA. The potential pathways of biomass pyrolysis with MC had also been proposed. In addition, the biochar obtained was utilized as a catalyst support of biochar-bearing sulfonic acid groups, which achieved the remarkable yields of TRS and glucose (52.8% and 43.5%) in hydrolysis of cellulose.


Assuntos
Sasa , Álcalis , Carbonatos , Celulose , Carvão Vegetal , Temperatura Alta , Hidrólise , Pirólise
16.
Proc Natl Acad Sci U S A ; 117(2): 883-888, 2020 01 14.
Artigo em Inglês | MEDLINE | ID: mdl-31888981

RESUMO

Phosphate is central to the origin of life because it is a key component of nucleotides in genetic molecules, phospholipid cell membranes, and energy transfer molecules such as adenosine triphosphate. To incorporate phosphate into biomolecules, prebiotic experiments commonly use molar phosphate concentrations to overcome phosphate's poor reactivity with organics in water. However, phosphate is generally limited to micromolar levels in the environment because it precipitates with calcium as low-solubility apatite minerals. This disparity between laboratory conditions and environmental constraints is an enigma known as "the phosphate problem." Here we show that carbonate-rich lakes are a marked exception to phosphate-poor natural waters. In principle, modern carbonate-rich lakes could accumulate up to ∼0.1 molal phosphate under steady-state conditions of evaporation and stream inflow because calcium is sequestered into carbonate minerals. This prevents the loss of dissolved phosphate to apatite precipitation. Even higher phosphate concentrations (>1 molal) can form during evaporation in the absence of inflows. On the prebiotic Earth, carbonate-rich lakes were likely abundant and phosphate-rich relative to the present day because of the lack of microbial phosphate sinks and enhanced chemical weathering of phosphate minerals under relatively CO2-rich atmospheres. Furthermore, the prevailing CO2 conditions would have buffered phosphate-rich brines to moderate pH (pH 6.5 to 9). The accumulation of phosphate and other prebiotic reagents at concentration and pH levels relevant to experimental prebiotic syntheses of key biomolecules is a compelling reason to consider carbonate-rich lakes as plausible settings for the origin of life.


Assuntos
Carbonatos/química , Lagos/química , Origem da Vida , Fosfatos/química , Apatitas , Cálcio , Dióxido de Carbono , Membrana Celular , Concentração de Íons de Hidrogênio , Minerais , Modelos Biológicos , Prebióticos , Rios , Solubilidade
17.
Chemosphere ; 246: 125789, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31918099

RESUMO

Salt pollution and anthropogenic-accelerated weathering is globally shifting the ionic composition and increasing salinisation of fresh water. We analyzed a 40-year data set (1970s-2010s) to characterize the drastic change of dissolved ionic composition, conductivity and pH levels. We also identified causative factors in these highly polluted mountain streams in northeastern China. Dissolved salt ions (Ca2+, Mg2+ and SO42-) increased by 3.02-5.21 fold and conductivity (a proxy for salinisation) increased by 3.09 fold. The average pH values increased from 7.08 to 8.49. The dominant ions, Ca2+, Mg2+, SO42- and HCO3- + CO32-, accounted for ∼90% of ionic composition based on mass concentration. Between the 1970s and 2010s, the dominant anion shifted from HCO3- + CO32- to a mixture of SO42- and HCO3- + CO32-. Increasing mining and land development appear to be the primary driving factors for the change of Ca2+, Mg2+, SO42- and HCO3- + CO32- concentrations; whereas, agricultural land was the main driving factor for the variation in K+, Na+ and Cl- concentrations. The source of ions has shifted from a more natural weathering of carbonate rocks to one of mineral dissolution that is affected by anthropogenic activities. Our study shows that freshwater mountain streams are at risk of long lasting anthropogenic salinisation and should be considered in future management and conservation plans.


Assuntos
Monitoramento Ambiental , Rios/química , Salinidade , Poluentes Químicos da Água/análise , Agricultura , Ânions , Carbonatos/química , China , Água Doce , Mineração , Tempo (Meteorologia)
18.
Environ Geochem Health ; 42(2): 579-599, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31444588

RESUMO

The present study region comprises granite and granite gneisses aquifer system constituted by Precambrian rocks. Groundwater is the primary source for drinking and other domestic purposes. Many developing regions in the world suffer from lack of safe drinking water. A rural part of Wanaparthy District in Telangana State, India, is one of them. For this reason, the groundwater samples collected from the study region were analyzed for pH, TDS, Ca2+, Mg2+, Na+, K+, HCO3-, Cl-, SO42-, NO3- and F- and evaluated groundwater quality criteria, using ionic spatial distribution (ISD), entropy water quality index (EWQI) and principal component analysis (PCA). The ISD maps show that some locations are not suitable for drinking purpose due to exceeding concentrations of TDS, Mg2+, Na+, K+, HCO3-, Cl-, NO3-and F-, compared to those with national drinking water quality standards. According to the EWQI, about 3%, 47%, 43% and 7% of the total area come under the excellent, good, medium and extremely poor water quality types for drinking purpose, respectively. Chadha's diagram classified the area as carbonate hardness (63%), non-carbonate alkali (17%), carbonates alkali (13%) and non-carbonate hardness (7%) zones. The binary diagrams (Na+ + K+ vs TC, Na+ vs Ca2+ and HCO3- vs TC) indicate that the quality of groundwater is controlled by influences of water-rock interactions, mineral weathering and dissolution, ion exchange and evaporation as well as the impact of anthropogenic sources. The PCA transferred the chemical variables into three principal components accounts for about 81% of the total variance. The high positive loadings of PC1 (Cl-, TDS, SO42-, Na+, NO3-, Mg2+ and HCO3-) stand for processes of silicate weathering and dissolution, ion exchange and evaporation, and the influence of domestic waste waters, irrigation return flows and chemical fertilizers on the groundwater system, the PC2 (F- and pH) signifies the alkaline nature of groundwater, which causes fluorosis, and the PC3 (K+) is a result of potassium fertilizers. The study helps to take remediate measures at a specific site and hence suggests the treatment of water before its drinking and also the recharge of the aquifer artificially to improve the groundwater quality.


Assuntos
Água Subterrânea/análise , Água Subterrânea/química , Qualidade da Água , Irrigação Agrícola , Carbonatos/análise , Água Potável , Entropia , Monitoramento Ambiental/estatística & dados numéricos , Fertilizantes , Hidrologia/estatística & dados numéricos , Índia , Análise de Componente Principal , Águas Residuárias , Poluentes Químicos da Água/análise , Qualidade da Água/normas
19.
Chemistry ; 26(2): 543-547, 2020 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-31691389

RESUMO

Herein, a visible-light photochemical approach for practical helicene functionalization at very mild reaction conditions is described. The photochemical reactions allow for the regiospecific and innate late-stage functionalization of helicenes and are easily executed either through the activation of C(sp2 )-Br bonds in helicenes using K2 CO3 as inorganic base or direct C(sp2 )-H helicene bond functionalization under oxidative photoredox reaction conditions. Overall, using these transformations six different functional groups are introduced to the helicene scaffold through C-C and four different C-heteroatom bond-forming reactions.


Assuntos
Luz , Compostos Policíclicos/química , Carbonatos/química , Catálise , Oxirredução , Potássio/química , Teoria Quântica
20.
ISME J ; 14(2): 425-436, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-31641279

RESUMO

Redox-active iron minerals can act as energy sources or electron-transferring mediators in microbial syntrophic associations, being important means of interspecies metabolic cooperation in sedimentary environments. Alkaline conditions alter the thermodynamic stability of iron minerals, influencing their availability for interspecies syntrophic interactions. We have modeled anaerobic alkaliphilic microbial associations in ethanol-oxidizing co-culture of an obligate syntroph Candidatus "Contubernalis alkalaceticum" and a facultative lithotroph Geoalkalibacter ferrihydriticus, which is capable of dissimilatory Fe(III) reduction and homoacetogenic oxidation of Fe(II) with CO2. The co-cultures were cultivated with thermodynamically metastable ferric-containing ferrihydrite, or ferrous-containing siderite, or without minerals. Mössbauer spectral analysis revealed the transformation of both minerals to the stable magnetite. In the presence of ferrihydrite, G. ferrihydriticus firstly reduced Fe(III) with ethanol and then switched to syntrophic homoacetogenesis, providing the growth of obligate syntroph on ethanol. The ability of G. ferrihydriticus to accept hydrogen from its syntrophic partner and produce extra acetate from carbonate during ethanol oxidation was confirmed by co-culture growth without minerals. In the presence of siderite, G. ferrihydriticus performed homoacetogenesis using two electron donors simultaneously- siderite and hydrogen. Pieces of evidence for direct and indirect hydrogen-mediated electron exchange between partner organisms were obtained. Relative abundancies of partner organisms and the rate of acetate production by their co-cultures were strongly determined by thermodynamic benefits, which G. ferrihydriticus got from redox transformations of iron minerals. Even the minor growth of G. ferrihydriticus sustained the growth of the syntroph. Accordingly, microbe-to-mineral interactions could represent underestimated drivers of syntrophic interactions in alkaline sedimentary environments.


Assuntos
Acetatos/metabolismo , Deltaproteobacteria/metabolismo , Compostos Férricos/metabolismo , Compostos Ferrosos/metabolismo , Firmicutes/metabolismo , Interações Microbianas , Minerais/metabolismo , Anaerobiose , Carbonatos/metabolismo , Deltaproteobacteria/crescimento & desenvolvimento , Etanol/metabolismo , Óxido Ferroso-Férrico/metabolismo , Firmicutes/crescimento & desenvolvimento , Oxirredução , Simbiose
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